Bonding efficiency of roller compacted concrete with different bedding mixes

Özcan, Sinan
Roller Compacted Concrete (RCC) has rapidly evolved from a concept to a material and a process which is used throughout the world for faster and more economical construction of dams. Currently, there are more than 250 RCC dams, completed or under construction, in the world. On the other hand, currently, there are only two RCC dams completed (Suçatı and Cindere Dams) and two under construction (Beydağ and Çine Dam) in Turkey. RCC dams are constructed in a series of compacted layers usually 30 cm in thickness. Therefore, appropriate bonding of successive layers is important and as a result, in between successive layers a bedding mix is often used to fill the surface voids in both the compacted layer below and the covering layer above, as well as to bond the two successive layers together. This study presents an experimental investigation on the bonding efficiency of RCC with different bedding mixes. The Beydağ Dam RCC mixture was taken as the model for the preparation of laboratory-made RCC specimens. In the experimental study, 15 cm cubic specimens were prepared in two layers. Each layer was compacted using an electro pneumatic demolition hammer for 30 seconds. Four different time intervals between placement and compaction of two successive layers and two different bedding mix types were the selected cases for investigation. While preparing the specimens, the second layer was placed and compacted 0, 4, 8, 12 and 16 hours after the first layer was compacted. In between the two layers, two types of bedding mixes are placed in between previously compacted and freshly placed layer for joint treatment. One of the bedding mixes, having 200 kg/m3 cement content is termed poor while other one is termed rich having 400 kg/m3 cement content. RCC specimens are then subjected to compressive strength, splitting tensile strength and permeability tests. As a result of the experimental program, it was found that; a rich bedding mix was a more effective bonding agent between compacted RCC layers than the poor bedding mix for all time intervals between layers. Furthermore, it was concluded that bonding efficiency of RCC is not too dependent on time interval between layer compactions up to 16 hours. Finally, splitting tensile strength and sorptivity tests are shown to be applicable test methods for determination of bonding efficiency of RCC specimens if there is a definite bedding layer in between freshly placed and formerly compacted RCC.


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Citation Formats
S. Özcan, “Bonding efficiency of roller compacted concrete with different bedding mixes,” M.S. - Master of Science, Middle East Technical University, 2008.